The antinoise barriers formed by panels that are located along roadway or railway communications to give acoustic protection to adjacent buildings are known.
Some kinds of opaque antinoise barriers comprise metal panels having one face, directed toward the noise source, made of perforated plate and housing materials with high acoustic absorbent characteristics, in particular mineral wool or glass wool. Indeed, it is known that sound energy, when incident on an acoustic absorbent surface, is absorbed in higher degree the higher is the coefficient of absorption of the material. In practice, the sound energy incident on these acoustic absorbent materials is transformed into heat because of the friction that is generated by the movement of the particles present in the interstices of the acoustic absorbent material hit by that energy.
Another type of barrier comprises instead transparent panels, in particular of glass, plexiglas, polymethyl methacrylate etc., which have acoustic insulation characteristics.
The inconvenience with the opaque barriers consists in compromising the luminosity of the buildings adjacent to the communication roads and in not allowing the view of the surrounding landscape.
The inconvenience with the barriers made of transparent panels consists in that, although offering sufficient acoustic insulation characteristics, they do not provide the absorption of sound waves. This can lead to an effect of acoustic reverberation toward the same noise source, which can have negative effects on the acoustic conditions of the zones contiguous to the transit roads and therefore limit the effectiveness of the barrier.